I was surprised to not find a comprehensive to getting all the different ending to this game, so decided to make my own.

Spoilers ahead, obviously.

These are the achievements that you get through regular game play.

Wobbly MK 2/3

Pick up your revolver at the beginning of the game.


Toil and Trouble

Find the bubble rounds at the Ossified Egg.

Cat Burglar

Find the grapple rounds at The Dump

Fire Bug

Purchase the fire rounds at Mazuma's shop.

Blast of Silence

Find the knockback rounds in Old Town by the Three Blind Mice.

Gumshoe

Find the explosive gum rounds in the gum factory.

Hot Tin

Find 10(?) tin voots. I don't think these have to be in the same save for all coin pickups.

Sterling

Find 5 silver voots.

Goldie

Find 3 golden voots.

Franky Hater

Shoot Franky at least 50 times. I think it has to be damaging rounds, ie not bubble rounds.

Flower Girl

Find all 16 flowers. I don't currently have a list of all the locations; some involve completing side quests.

I Would Walk 500 Miles

Walk around for 500 miles; basically until the achievement pops.

I Would Walk 500 More

As the name implies, walk a further 500 miles for a total of 1000 miles.

Four different vignettes play during the epilogue (before the credits), and each one can be different based on which search/arrest warrants you obtain and which clues you find. Easiest way to do this is to save in the bathroom right before confronting Shelly and Buttons.

They Were Never Here

Finish the game without the Penthouse Heist arrest warrant or the Leo's Murder arrest warrant.

They Got Off Easy

Finish the game with the Penthouse Heist arrest warrant but without the Leo's Murder arrest warrant.


They Went Away

Finish the game without the Complicity arrest warrant but with the Leo's Murder arrest warrant.

They Cut A Deal

Finish the game with the Complicity arrest warrant and the Leo's Murder arrest warrant.

Business As Usual

Finish the game without the Complicity Arrest warrant. This requires choosing the option to fabricate evidence in the final conversation.

The Middle Manager
Finish the game with the Complicity search and arrest warrants but without the evidence of collusion between Shelly and Adrien (from Mazuma's shop or the safe in the Penthouse).


The Fall Guy

Finish the game with the Complicity search warrant but without the Complicity arrest warrant.

The Deathbed Conversion
Finish the game with the Complicity search and arrest warrants and the evidence of collusion between Shelly and Adrien (from Mazuma's shop or the safe in the Penthouse).

A Milk Dish Served Cold
Finish the game without the Complicity arrest warrant. This requires forcing your way back into the Penthouse by threatening to use gum rounds on the doorman and fabricating evidence against Button.

Like A Cat

Finish the game with both the Complicity arrest warrant and the evidence of collusion between Shelly and Adrien (from Mazuma's shop or the safe in the Penthouse).

Bad Kitty

Finish the game with the Complicity arrest warrant but without the evidence of collusion between Shelly and Adrien (from Mazuma's shop or the safe in the Penthouse).

Loose Cannon

Finish the game without any arrest warrants. Force your way up into the Penthouse and fabricate evidence against Button.

Gumshoe

Finish the game with the Penthouse Heist arrest warrant but without any others.


American Pie

This vignette has several possible ways to achieve it.


Finish the game without the Penthouse Heist arrest warrant but with the Leo's Murder arrest warrant and the evidence of collusion between Adrien and Shelly.

OR

Finish the game without the Leo's Murder arrest warrant or the evidence of collusion between Adrien and Shelly but with the Complicity Arrest warrant.

OR

Finish the game with the Leo's Murder arrest warrant but without the evidence of collusion between Adrien and Shelly or the Complicity Arrest warrant.

Bubble Vacation

Finish the game with the Penthouse Heist Arrest warrant, the Leo's Murder arrest warrant, and the evidence of collusion between Adrien and Shelly. Basically get every warrant and clue you possibly can.

These achievements are not tied to any particular vignette during the Epilogue.

Employees Are Required

Wash your hands at the sink every time you use the toilet to save, before leaving. The global flag "dirtyHands" is used to check this.

Best Buddies

Beat the game without Franky going to jail. This means you cannot talk to Adrien Fois as Franky will go to jail even if you already have the arrest warrant for Buttons. This means you either have to find the clues for Buttons arrest warrant without talking to Adrien, or use threats to make your way back into the Ossified Egg.

Key To Executive Washroom

At the time of writing this guide this achievement was impossible to achieve with out "extreme measures". It apparently relates to a game the dev has not actually yet made.

Feel free to leave a comment if you come upon any errors. I haven't verified everything so take this as more of a guide then absolute truth.

I compiled this guide using my memories of playing the game and tools to poke around the game files to get the exact conditions required to get each vignette. I won't lay out exactly how to do this but it's a Unity game so you can start from there if you really want to find out how. Similarly, since it's a Unity game the save files are stored in the registry so you can edit your saves if you reallllly want to, but I'm making no guarantees there.